In scenarios where poor soil exists at shallow depths, or where large loads are contemplated, deep foundations may be advantageous. These foundations are effective at handling larger loads and provide lateral resistance. Bored piers and piles refer to types of foundations that are constructed by drilling into the earth and subsequently placing materials with stronger compressive strength in the excavation to form a foundation unit. These foundations are often referred to collectively as drilled-shaft foundations. The materials used traditionally to form these pier systems are concrete, steel, and cement grout. For example, in a typical drilled shaft foundation, an auger is used to drill a hole of planned diameter to the design depth. Then a full-length reinforcing steel frame is lowered into the hole and the hole is subsequently filled with concrete. The reinforced caisson, as it is sometimes called, can be used to support heavy loads like buildings, bridges, towers, etc. It resists compressive and lateral loads, as well as uplift tendencies.
Unfortunately, existing construction methods suffer certain drawbacks. For example, the materials currently used, such as concrete and steel, themselves add significant weight to an already weak soil system. In addition, construction of individual piers is time consuming and difficult in the face of certain ground conditions such as excessive free water. Likewise, cure time for concrete and cement grout delays the time until the foundation can be loaded. Delays such as these are significant drawbacks where the above structure is in use, such as with a highway. A need exists for a rapid pier system and method that can be put in place in less time with less weight, but still offer high strength and bearing capacity.